The invention involves a method of designing and making lenses with simpler surfaces based on lenses with more complex surfaces. The manufacture of contact lenses with two complex surfaces is complicated, costly, and requires extremely precise mechanical tolerances. This is particularly true in the case of non-rotationally symmetric surfaces. Simple surfaces such as spherical and toroidal forms reduce design and manufacturing difficulties. Converting complex surfaces into an optically equivalent lens design which has a single complex surface and a simple surface design would thus be beneficial.
The surface topography of most human corneas is not spherical and typically changes at varying, unpredictable and unique rates from the center of the cornea out to the periphery in a manner that is often quite complex. Lens designs made to account for these effects can involve complex geometries on both front and back surfaces. For example, a cornea with several different astigmatic aspects or higher order aberrations may compel a lens design with many irregular surfaces on both the front and back surfaces of the lens. Where these lenses are soft contact lenses this greatly complicates their manufacture. It also ironically adds a degree of unpredictability in that a complex back surface can alter the on-eye characteristics of the lens in a way that detracts from the optical effect the lens would ideally have.
This complexity is even more likely in modern lens design that seeks to integrate corneal topographic data and ocular wavefront data with primary ametropia measurements. As more of this type of information is used in lens design and manufacture the likelihood of obtaining a complex design that could produce excellent visual results but which are very difficult to manufacture increases. It is thus desirable to find simple lens designs that are optically equivalent or nearly equivalent to those complex designs.